The present invention pertains to a platen press for compressing a product, such as particleboard, copper laminate or the like, and a control for computing and regulating the loads on the frame plates of the press to attain uniform thickness of the product.
In both single and multiple opening presses, the bolster and/or several platens forming the openings are carried by two or more uprights. These uprights are spaced-apart frame plates located at opposed longitudinal ends of the platens. Hydraulic cylinder assemblies are provided in the frames to bring the bolsters together to close the press and to apply the required pressure distribution to compress the product. The distance between the two or more frame plates with their respective cylinders is normally set up to accommodate the maximum length of the product. The bolsters through the cylinders compress the product to a substantial uniform thickness.
In this arrangement for a press problems arise with non-uniform loading on the bolsters caused by a product shorter in length than that of the bolsters and platens. In pressing the shorter lengths, especially in a single opening press with an upper and lower bolster, the amount of deflection along the bolsters varies between a minimum and maximum deflection. The deflection curve for the top and bottom bolsters either results in being a mirror image or the reversal of each other, where heavier loads may exist at the ends of the bolsters with lighter loads in the center, or vice versa.
Deflection of this type results in non-uniformity of product thickness. This requires grinding to obtain a uniform product thickness after the pressing process. This leads to excessive loss of time, waste of material, and expense in both labor and equipment, which is totally unacceptable to the particle board and laminate industry.